In general, traditional telephone networks, such as the publicly-switched telephone network (“PSTN”), employ circuitry and switches to connect telephone users across the PSTN to facilitate communication. The PSTN employs the International Telecommunication Union standard Common Channel Signaling System # 7 (SS7) for call setup, call routing, and control of other PSTN components for calls worldwide. Networks that employ SS7 signaling protocols are referred to herein as SS7 networks.
An emerging alternative to traditional phone networks uses packetized data to transmit content of telephone communications (e.g., voice or videoconferencing data) through data networks, such as packet-based networks and/or broadband networks. Data networks employ data transfer protocols such as Internet Protocol (IP) to support voice, data, and multimedia (e.g., video) content. Transmitting telephone communications over the Internet is commonly referred to as a Voice over Internet Protocol (VOIP). Transmitting telephone communications over other broadband networks can be referred to as Voice Over Broadband (VOBB). A packet-based telephone network employs packet-switches (also referred to herein as gateways, media gateways, media gateway controllers, switching components, softswitches, data sources, or call processors). A packet assembler can convert a signal received from a traditional telephone network call into a set of data packets for transmission through the IP network.
Routing telephone calls over a data network involves interfacing the PSTN to the data network. FIG. 1 is a known architecture developed by Sonus Networks, Inc. for interfacing the PSTN to a data network. FIG. 1 depicts a system 100 that includes a signaling network 105 that provides PSTN signaling, for example, SS7 signaling, that is associated with a particular telephone call. The SS7 signaling includes out-of-band messages and instructions for routing the content of the phone call that is received from a first PSTN (not shown). The first PSTN is associated with the signaling network 105 and can include the signaling network 105. The signaling network 105 communicates with a signaling gateway 110 over a communication path 115. The communication path 115 can be, for example, a time-division multiplexed path for providing signaling information and/or the call content to the signaling gateway 110. One example of a signaling gateway is a SGX, sold by Sonus Networks Inc.
The signaling gateway 110 determines where to transmit the call content based on the signaling information. The signaling gateway 110 is in communication with a media gateway 120 over a communication link 125 through a packet-based network 130. One example of a media gateway is a GSX9000, sold by Sonus Networks Inc. The call content is provided to the media gateway 120 by the first PSTN. The signaling gateway 110 transmits packet-based signaling with the call content to the media gateway 120. The packet-based signaling is used to route the call content through the packet-based network 130 to the media gateway 120 and allows the media gateway 120 to transmit the call content to the PSTN 135. The media gateway 120 also provides PSTN signaling to the PSTN 135 to allow the PSTN 135 to deliver the call content to the appropriate telephone 140.
The system 100 also includes a controller 145 in communication with the media gateway 120 and other media gateways (e.g., the media gateway 150). One example of a controller is a PSX, sold by Sonus Networks Inc. The controller 145 provides routing and policy information to the media gateway 120 for processing the call content and packet-based signaling information. Congestion or a high-volume of call traffic that occurs on either the SS7 network 105 or on the packet-based network 130 can affect call quality (e.g., the number or rate of dropped calls or echo effects).
FIG. 2 is a block diagram of a known configuration for providing redundancy in telephone networks. The system 200 includes a signaling network 205 that communicates with a first server 210 over a first communication path 215 (e.g., a TDM signaling link). The signaling network 205 also communicates with a second server 220 over a second communication path 225. The first server 210 communicates with a second server 220 over an inter-server communication path 230.
The first server 210 and the second server 220 are logically associated with a switch 240. The inter-server communication path 230 facilitates load-sharing between the first server 210 and the second server 220. The first server 210 and the second server 220 each handle about one-half of all calls that are handled by the switch 240. In some embodiments, the first server 210 represents a first computing element CE0 to a packet-based network (not shown), and the second server 220 represents a second computing element CE1 to the packet-based network.
If the first server 210 fails, the capacity of the switch 240 to process calls is reduced by about one-half. Similarly, if the second server 220 fails, the capacity of the switch 240 to process is reduced by about one-half. Moreover, upgrading the software of either the first server 210 or the second server 220 involves taking the particular server out of service. As a result, the number of calls processed by the switch 240 is reduced by about one-half.